Compliant, strain tolerant interconnects for solid oxide fuel cell stack

ABSTRACT

An interconnect for a solid oxide fuel cell includes a compliant superstructure having a first portion defining a separator plate contact zone and a second portion defining an electrode contact zone, wherein the super structure is porous. In one embodiment, the superstructure is defined by a plurality of compliant substructures provided in a first direction and a plurality of compliant substructures provided in second direction to define a woven structure.

CROSS-REFERENCE TO RELATED CASES

[0001] This application claims the benefit of earlier-filed provisionalpatent applications entitled, “Compliant, Strain Tolerant Interconnectsand Seals for Solid Oxide Fuel Cell Stack,” Application No. 60/444,025,filed Jan. 31, 2003, and “Compliant Interconnects and Seals for SolidOxide Fuel Cell Stack,” Application No. 60/454,899, filed Mar. 14, 2003,and is a continuation-in-part of U.S. application Ser. No. 10/307,008,Filed Nov. 27, 2002.

BACKGROUND OF THE INVENTION

[0002] The invention relates to solid oxide fuel cell (SOFC) stacks and,more particularly, to an interconnect that enhances the lifetime of SOFCstacks.

[0003] A fuel cell is a device which electrochemically reacts a fuelwith an oxidant to generate a direct current. The fuel cell typicallyincludes a cathode, an electrolyte and an anode, with the electrolytebeing a non-porous material positioned between the cathode and anodematerials. In order to achieve desired voltage levels, such fuel cellsare typically connected together using interconnects or bipolar platesto form a stack, or fuel cell stack, through which fuel and oxidantfluids are passed. Electrochemical conversion occurs, with the fuelbeing electrochemically reacted with the oxidant, to produce a DCelectrical output.

[0004] The basic and most important requirements for the interconnectmaterials on the cathode side of a SOFC stack are sufficient oxidationand corrosion resistance in air at the stack operating temperatures;sufficient electron conductance; and close matching of thermal expansionbehavior to that of the ceramic cell. In the case of metallicinterconnects, the requirement of sufficient electron conductance isessentially equivalent to the electron conductance of the oxide scalethat forms on the metal surface because the oxide scale tends to be thelimiting resistance. Currently, the lack of stable, long-life (>40,000hours), metallic interconnects for the cathode side of the stack, is aserious weakness of planar solid oxide fuel cells, because existingmetal alloys cannot meet the thermal expansion, oxidation resistance,and electron conductance requirements simultaneously.

[0005] Cathode interconnect materials that have been used to dateinclude perovskite-based ceramics, e.g. lanthanum chromite, hightemperature chromium-based alloys or composites thereof, andnickel-based alloys or intermetallics have been used typically for cellsoperating in the 800-1000° C. range.

[0006] The prior art on ceramic-based interconnects such as lanthanumchromite indicates that this material exhibits both usable hightemperature conductivity and thermal expansion behavior that matches thecell. However the ceramic is very expensive, has low toughness and isdifficult to manufacture as a suitable interconnector. Chromium-basedinterconnector materials have similar drawbacks.

[0007] Lower operating temperatures, (650-800° C.) with planaranode-supported cells, permit use of lower cost materials such asferritic stainless steels that have a better coefficient of thermalexpansion (CTE) match with the cell than Ni-based alloys. Commercialgrades of ferritic steels may have suitable oxidation resistance attemperatures less than about 600° C. or for short lifetimes, but do nothave the required oxidation resistance to last for 40,000 hours, orlonger, due to the increasing ohmic resistance across the oxide scalewith time under load.

[0008] The majority of prior art on these issues has attempted toprevent or ameliorate the degradation caused by oxide scale.Specifically, to take advantage of the lower cost and favorable CTE offerritic steels, minor alloying additions and/or surface coatings havebeen researched to improve the oxidation resistance and conductivity.Certain elements such as Mn appear beneficial in forming manganesechromite which increases the conductivity of the oxide scale, but moredata is needed to determine whether both conductivity and oxidationresistance are sufficient for long-term applications. However, elementsknown to improve oxidation resistance, such as Al and Si, also tend todisadvantageously reduce the oxide conductivity and increase the CTE ofthe alloy. In Fe—Cr—Al—Y type steels, excellent oxidation performance istraded for the high resistivity of the resulting alumina film. Hence,the current state-of-the-art with regard to low cost Fe—Cr-based steels,has not fully resolved the long-term contact and oxidation issues.

[0009] Other materials, such as Ni—Cr or Ni—Cr—Fe-based alloys, whilehaving good oxidation/corrosion resistance by design, typically have CTEvalues in the 15-18 parts per million (ppm)/° C. compared to the about12 ppm/° C. of ferritic steels which better match the CTE of the ceramiccell.

[0010] Preferential removal of the oxide and/or coating/doping of thealloy surface with noble metals such as Ag, Au, Pt, Pd, and Rh has beenused to mitigate conductivity loss by reducing oxygen diffusion into thecontact points of the interconnect, but noble metals are too costly touse in power plants and commercial applications.

[0011] The oxidation resistance is clearly a concern on thecathode/oxidant side of the interconnect. However, the partial pressureof oxygen at the anode/fuel electrode may also be high enough to formCr₂O₃ and the oxide may be even thicker (viz. the presence ofelectrochemically formed water) than on the cathode side of theinterconnect, so the resistivity of the interconnect may increase onboth sides. The construction materials on the anode side of theinterconnect could be the same as the cathode, although prior art hasshown that, in the case of a ferritic steel interconnect in contact witha nickel anodic contact, weld points that formed between the steel andthe nickel still formed a thin electrically insulating Cr₂O₃ layer overtime which degraded performance.

[0012] It is clear, from the above review of background art, that theneed remains for a substantially improved interconnect between adjacentcells, whereby interface strains, caused by CTE mismatch during thermalcycling, are substantially eliminated, while the material provideslong-term oxidation resistance and high electron conductance across theoxide scale.

[0013] It is therefore the primary object of the present invention toprovide an interconnect or bipolar plate that meets the aforementionedneeds.

[0014] Other objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

[0015] In accordance with the present invention, the foregoing objectsand advantages have been readily attained.

[0016] The present invention provides a solid oxide fuel cell designhaving a compliant porous interconnect which alleviates the thermalexpansion mismatch stresses which are typically generated by higherthermal expansion oxidation resistant interconnect metals and/or alloysfor the cathode.

[0017] The interconnect of the present invention advantageously allowsfor the use of higher thermal expansion oxidation resistant metals oralloys for the separator plate.

[0018] The interconnect of the present invention further advantageouslyallows for less stringent dimensional tolerances of the stack componentssince the interconnect is compliant in all three dimensions and permitsdisplacement with minimal increase in stress to accommodate dimensionalvariations.

[0019] According to the invention, an interconnect is provided whichcomprises a compliant porous member, compliant in all three-dimensionsand having first portions defining a separator plate contact zone andsecond portions spaced from said first portions and defining anelectrode contact zone.

[0020] In further accordance with the invention, an interconnectassembly is provided for solid oxide fuel cells, which assemblycomprises a separator plate having two opposed surfaces; and at leastone interconnect positioned adjacent to at least one of said two opposedsurfaces and comprising a compliant porous member, compliant in allthree-dimensions and having first portions defining a separator platecontact zone and second portions spaced from said first portions anddefining an electrode contact zone.

[0021] Still further according to the invention, the interconnectassembly could be comprised of one or more layers, at least one of whichis compliant as described herein. In this embodiment, the compliantlayer may or may not be in contact with the separator plate or theelectrodes.

[0022] Still further according to the invention, a solid oxide fuel cellassembly is provided which comprises a plurality of fuel cells arrangedin a stack; and a plurality of interconnect assemblies positionedbetween adjacent cells of said stack, said interconnect assembliescomprising a separator plate having two opposed surfaces and at leastone interconnect positioned adjacent to at least one of said two opposedsurfaces and comprising a compliant porous member, compliant in allthree dimensions and having first portions defining a separator platecontact zone and second portions spaced from said first portions anddefining an electrode contact zone.

[0023] Particularly desirable configurations of the interconnect involvethree-dimensional compliant superstructures made out of wire weaves orother compliant sub-structures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] A detailed description of preferred embodiments of the presentinvention follows, with reference to the attached drawings, wherein:

[0025]FIG. 1 schematically illustrates a fuel cell stack assembly inaccordance with the present invention;

[0026]FIG. 2 schematically illustrates a portion of the fuel cell stackassembly of claim 1;

[0027]FIG. 3 illustrates a preferred embodiment of an interconnect ofthe present invention;

[0028]FIGS. 4 and 5 illustrate another preferred embodiment of aninterconnect of the present invention;

[0029]FIG. 6 illustrates an alternate embodiment of an interconnect ofthe present invention;

[0030]FIG. 7 illustrates an alternate embodiment of an interconnect ofthe present invention;

[0031]FIG. 8 illustrates another alternate embodiment of an interconnectof the present invention;

[0032]FIG. 9 illustrates a wire structure with compliance loopsaccording to the invention; and

[0033]FIG. 10 illustrates another preferred embodiment of aninterconnect of the present invention.

DETAILED DESCRIPTION

[0034] The invention relates to a fuel cell assembly and, moreparticularly, to a solid oxide fuel cell (SOFC) stack having improvedmetallic interconnect which decouples the need for good coefficient ofthermal expansion (CTE) match with other stack components from otherrequirements such as oxidation resistance and oxide scale electronconductance.

[0035] The invention relates further to a fuel cell stack and, moreparticularly, to a solid oxide fuel cell stack having an improvedinterconnect, whereby stresses due to difference in thermal expansioncoefficient between adjacent fuel cell stack components, andspecifically between the cathode or anode interconnect and adjacent fuelcell or separator plate, are minimized so as to provide for enhancedfuel cell stack lifetime and robustness under steady state and thermalcycling.

[0036] Reduction in stress is accomplished through a compliantinterconnect superstructure provided from a compliant sub-structure,wherein the interconnect superstructure is provided having contours soas to define spaced contact zones for contacting a separator plate onone side and an electrode of a fuel cell on the other side, and thesub-structure is provided by highly compliant pre-buckled architectureas present in a wire mesh. The combination of the two, compliantsuperstructure and compliant sub-structure, providing spaced contactzones in accordance with the present invention advantageously allows forCTE mismatch between various components of the stack without subjectingsuch components, or bonds or other types of connection therebetween, toexcessive stress, while improving fluid flow and electricalfunctionality of the fuel cell.

[0037] The compliant interconnects described herein are designed suchthat high values of both in-plane and out-of-plane compliance areachieved. One skilled in the art will recognize that any suchinterconnect that provides for acceptable levels of either in-planecompliance or out-of-plane compliance, or both, will be within the broadscope of the invention. Preferably, the compliant superstructure iscompliant in at least three orthogonal axes, and is compliant withrespect to a load applied from any direction. Various approaches toachieve this include wire weave based superstructures as describedabove, 3-dimensional knitted wire structures, helical coils in variousconfigurations including slanted helical coils provided by pre-buckledhighly compliant sub-structures, wires with in-built highly compliantcompliance loops, similar interconnects made from sheet metal, foil,foam, or expanded metals formed into superstructures, etc. Preferredcompliance values of the interconnects are 5×10⁻⁶ mm²/N (instrain/stress units) and higher for typical interconnects at roomtemperature. More preferred compliancy values are 5×10⁻⁵ mm²/N andhigher for typical interconnects. Most preferred compliancy values are5×10⁻⁴ mm²/N and higher for typical interconnects, but one of ordinaryskill in the art will recognize that other compliancy values can beacceptable and are within the scope of the invention.

[0038] Turning to FIG. 1, a fuel cell stack assembly 10 in accordancewith the present invention is schematically illustrated. Assembly 10preferably includes a plurality of fuel cells 12 arranged in a stackwith bipolar plates 14 positioned therebetween.

[0039] Fuel cells 12 typically include an electrolyte 16, a cathodelayer 18 positioned on one side of electrolyte 16, and an anode layer 20positioned on the other side of electrolyte 16. Bonding or currentcarrying layers 22 may be used on the two sides.

[0040] Bipolar plate 14 in accordance with the present inventionadvantageously includes a separator plate 24 having a cathode facingsurface 26 and an anode facing surface 28, a cathode-side interconnect30 positioned between cathode facing surface 26 and a cathode layer 18(or layer 22) of an adjacent fuel cell 12, and an anode-sideinterconnect 32 positioned between anode facing surface 28 and an anodelayer 20 (or layer 22) of an adjacent fuel cell 12. Interconnects 30, 32are advantageously provided of an electron conducting material and arein electrical communication with separator plate 24.

[0041] Referring to FIG. 2, a particular aspect of the present inventionis the design of cathode-side and anode-side interconnects 30, 32,wherein the interconnects are provided as a sheet of woven wire materialformed to have a plurality of first portions 34 or 38 defining anelectrode contact zone, and a plurality of second portions 36 defining aseparator plate contact zone which is spaced from the electrode contactzone.

[0042] Still referring to FIG. 2, interconnects 30, 32 in accordancewith the present invention, especially cathode-side interconnect 30,consists of compliant sub-structure, preferably wire weaves, material asdescribed above which is formed, for example through die stamping,rolling, bending or the like, to have a three-dimensional superstructuredefining first and second portions 34, 36.

[0043] The compliant wire weave sub-structure of interconnects 30, 32 inaccordance with the present invention is advantageously a wire weavesuch as that illustrated in FIG. 2, which advantageously provides apre-buckled architecture that increases compliance of interconnect 30,32. This compliance allows for movement or deflection without stressingof first portions 34, relative to second portions 36 during thermalcycling and the like, which advantageously serves to eliminate stressescaused by CTE mismatch between various components. The compliantinterconnects formed from such sub-structures and superstructures alsoadvantageously allows for movement between first portion 34 with respectto second portion 36 without stressing during assembly, therebypermitting larger dimensional tolerance variations.

[0044] The wire weave as shown in FIG. 2 may include a first pluralityof wires or substructures disposed in one direction, and a secondplurality of wires or substructures disposed in a different direction,so as to define a woven wire structure which is porous to operating fuelcell gaseous materials and compliant as desired in different directions,in accordance with the present invention.

[0045]FIG. 3 shows a perspective view of an interconnect 30, 32 tofurther illustrate a preferred sub-structure and superstructure thereof.

[0046]FIGS. 1, 2 and 3 illustrate interconnects 30, 32 as members havinga substantially sinusoidal cross section, wherein peaks 38 on one sideof a centerline 40 define the electrode contact zone, and peaks 42 onthe other side of centerline 40 define the separator plate contact zone.In accordance with a preferred aspect of the present invention, and asillustrated in FIG. 3, the undulating or vertically contoured shape ofinterconnect 30, 32 extends in the transverse direction to the crosssection illustrated in FIGS. 1 and 2 so as to define a series of spacedpeaks 38, 42, each extending in opposite directions from centerline 40,so as to define the spaced contact zones discussed above.

[0047] It should of course be appreciated that other architectures couldbe provided for interconnects 30, 32, within the broad scope of thepresent invention, which could equally provide for the spaced contactzones connected by compliant members which provide for advantageousreduction in stresses between components as desired in accordance withthe present invention.

[0048]FIG. 4, for example, illustrates interconnect 30, 32 withcompliant superstructures shaped in a substantially orthogonal, forexample square or retangular channel pattern, made from a compliantsub-structure material, preferably wire weave, wherein the interconnectsform spaced contact zones in the cross sectional view. FIG. 4 furtherillustrates a preferred wire weave structure according to the invention.FIG. 5 shows a perspective view of such an interconnect 30, 32 onbipolar plate 14.

[0049] Another example, FIG. 6, shows a substantially square channeledsuperstructure interconnect 30, 32 with spaced contact zones present inboth the cross sectional and the transverse direction.

[0050] Another example, FIG. 7, shows a substantially trapezoidalsuperstructure interconnect 30, 32 made from compliant sub-structures.

[0051] Another example, FIG. 8, illustrates a superstructureinterconnect 30, 32 made into a circular or a helical, preferablyslanted, structure wherein a compliant sub-structure such as apre-buckled wire or wire weave forms the three-dimensionalsuperstructure.

[0052]FIG. 9 illustrates an embodiment wherein wires 52 are providedwith compliance loops 54 as described above. This structure serves toenhance the ability of the wire to resiliently deform as needed torespond to different CTE, and also to provide desired manufacturingtolerances. This compliance loop structure can be incorporated into thesubstructure and/or the superstructure of the interconnect of thepresent invention.

[0053]FIG. 10 shows a substantially hour-glass shaped superstructureinterconnect 30, 32 made from compliant sub-structures.

[0054] Interconnect 30, 32 in these examples can be positioned betweencomponents of the stack in similar fashion to the embodiment describedabove in connection with FIGS. 1-4.

[0055] Clearly, those skilled in the art will realize that a largenumber of patterns and arrangements of such compliant sub-structures aswell as superstructures exist, and are all within the broad scope of thepresent invention.

[0056] Different materials and architectures may be desirable forcathode-side interconnect 30 than for anode-side interconnect 32.

[0057] Cathode-side interconnect 30 is preferably provided having thearchitecture as described above and illustrated in FIGS. 1 and 2.

[0058] Anode-side interconnect 32 can advantageously be provided havingthe same architecture, or having a foam architecture defining foam cellswhich, themselves, define the contact zones for contact on one side withseparator plate 24 and on the other side with the anode of a fuel cell12.

[0059] Further, in the cathode environment, it is desirable to providecathode-side interconnect 30 of an oxidation resistant conductivematerial, preferably of a material selected from the group consisting ofselected stainless steels, stainless steel alloys and super-alloyscomprising Ni—Cr—, Ni—Cr—Fe—, Fe—Cr—, Fe—Cr—Ni and Co-based alloys aswell as Cr-based alloys and noble metal/alloys. Such super-alloysinclude HAYNES® alloy 230, HAYNES® alloy 230-W, and Hastelloy X, whichhave been found preferable in the present invention. Other materialsinclude composites of at least 2 materials, for example metals andceramics containing any of the above mentioned metals and alloys.Another set of materials include noble metal coated super-alloys.

[0060] Anode-side interconnect 32 is advantageously provided of amaterial selected from the group consisting of Ni, Ni—Cu, Ni—Cr—,Ni—Cr—Fe—, Fe—Cr—, Fe—Cr—Ni and Co-based alloys as well as Cr-basedalloys and noble metal/alloys and including such alloys coated with Ni,Cu or Ni—Cu as well as noble metals. Other materials include compositesof metals and ceramics containing any of the above mentioned metals andalloys.

[0061] In accordance with the present invention, interconnects 30, 32when provided having the configuration of FIGS. 1 and 2 preferablydefine a superstructure wherein peaks 38, 42 define a superstructurewavelength of between 0.1 mm and 100 mm, a superstructure amplitude ofbetween 0.1 mm and 50 mm, and a superstructure periodicity which may beuniform or random.

[0062] Further, the wire weave sub-structure of interconnect 30, 32 inaccordance with the present invention is preferably provided having awire diameter of between 0.05 mm and 5 mm, a sub-structure weavewavelength of between 0.05 mm and 50 mm, a weave amplitude of between0.05 mm and 50 mm, a weave pattern which may be square, plain, satin,twill or other patterns, and a weave periodicity which may be uniform orrandom.

[0063] In addition, the wire weave sub-structure of interconnect 30, 32may be composed of wires of different diameters and/or alloys indifferent places to facilitate functionality.

[0064] In accordance with the present invention, separator plate 24 canadvantageously be bonded to anode-side interconnect 32 and cathode-sideinterconnect 30 through various methods to produce high-strengthinterfaces therebetween. For example, such joints or components can bebonded, welded or brazed together, or can be secured together in othermanners which would be well known to a person of ordinary skill in theart. Furthermore, it is within the broad scope of the present inventionto position these components adjacent to each other without any bondingtherebetween.

[0065] The wire weave sub-structure and three-dimensional superstructureof the interconnects in accordance with the present inventionadvantageously serves to alleviate stresses at the anode and cathodeinterfaces, and minimizes fracture of the interface and the cellsthemselves.

[0066] In further accordance with the present invention, and asillustrated in FIG. 1, a compliant seal is further advantageouslyprovided for sealing between edges of bipolar plate 14 and adjacent fuelcells 12.

[0067] In accordance with the present invention, the seal design isprovided in the form of a rail or spacer 44 defining therein a groove46, and a seal member 48 positioned in groove 46 and compressed betweenbipolar plate 14 and adjacent fuel cells 12 to provide the desired sealtherebetween. A compression stop 50 is provided to control the amount ofdeflection of the compliant seals and to advantageously assemblecompliant interconnects, compliant seals and all other elements of thestack.

[0068] In further accordance with the present invention, seal member 48is advantageously provided as a compliant or compressible member formedfrom a suitable material, preferably alumina fibers. Alumina is mostdesirable in accordance with the present invention because alumina doesnot contaminate the fuel cell as do other seal materials which haveconventionally been used, such as glass, glass-ceramics and the like.

[0069] Thus, in accordance with the present invention, seal member 48 isadvantageously provided as compliant alumina fibers which can preferablybe impregnated with another material selected so as to providesubstantial gas impermeability of seal member 48 while neverthelessallowing for compliance or compressibility thereof.

[0070] The seal member 48 in accordance with the present invention canadvantageously be impregnated with a material selected from the groupconsisting of zirconia, alumina, yttrium aluminum garnate,alumino-silicate and magnesium silicate ceramics, and similar oxides,and combinations thereof, and it is preferred that seal member 48 beprovided so as to reduce permeability to gas.

[0071] Seal member 48 can advantageously be provided having a fiberarchitecture such as tows, yarns, fiber weave architecture and the like.Such architectures can be loaded with secondary particles within thefibers as discussed above so as to provide desired seal properties.Further, rail/spacer 44 and compression stop 50 is provided having aheight and groove depth which are selected to provide for additionaldecoupling of various parameters which are conventionally required to berelated.

[0072] It should be noted that a significant parameter is the responseof the interconnect and seal to the clamping compressive load which mustbe applied to the fuel cell stack as schematically illustrated in FIG.1.

[0073]FIG. 1 shows a compressive load applied to the top and bottom ofassembly 10 which compressive load is advantageously selected to providefor sufficient interconnect bonding and sufficiently reduced leakage inthe seals while nevertheless allowing micro-sliding in the seal area torelieve thermal mismatch stresses and to minimize compressive creep ofthe interconnects.

[0074] From a manufacturing standpoint, the system of the presentinvention provides for cells and interconnects having less stringentdimensional tolerances since the interconnect provides out-of-planecompliance and, therefore, increased dimensional freedom. Further, theprovision of fixed thickness rail/spacers 44 and compression stops 50ensures decoupling of the sealing and interconnection requirements andtherefore provides substantial flexibility for building stacks that arebased upon stable and compatible materials.

[0075] It should of course be appreciated that in accordance with thepresent invention, an interconnect superstructure and compliant sealassembly have been provided which advantageously allow for reducedstringency in tolerances in manufacture and assembly of solid oxide fuelcell stacks, and further which reduce the stresses conveyed betweenvarious components of the stack, thereby advantageously decouplingdifferent design concerns of the stack and allowing selection ofmaterials to provide long stack life.

[0076] It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope.

What is claimed is:
 1. An interconnect assembly for a solid oxide fuelcell, comprising: a separator plate having two opposed surfaces; and atleast one electron conducting compliant interconnect in electricalcommunication with the separator plate, the compliant interconnectcomprising a compliant superstructure having a first portion defining aseparator plate contact zone and a second portion defining an electrodecontact zone, wherein the superstructure is porous to operating fuelcell gaseous materials.
 2. The assembly of claim 1, wherein saidcompliant superstructure is compliant in at least three orthogonal axes.3. The assembly of claim 1, wherein said compliant superstructure iscompliant with respect to a load applied from any direction.
 4. Theassembly of claim 1, wherein said compliant superstructure comprises afirst plurality of compliant substructures disposed in a first directionand a second plurality of compliant substructures disposed in a seconddirection different from said first direction so as to define a wovenstructure.
 5. The assembly of claim 4 wherein at least one compliantsubstructure is pre-buckled.
 6. The assembly of claim 4 wherein saidcompliant substructures comprise wires, and wherein said woven structureis a wire weave.
 7. The assembly of claim 4 wherein said compliantsubstructures comprise pre-buckled wires, and wherein said wovenstructure is a wire weave.
 8. The assembly of claim 4 wherein saidcompliant superstructure is dimpled, and wherein further a firstplurality of dimples define said separator plate contact zone and asecond plurality of dimples define said electrode contact zone.
 9. Theassembly of claim 8 wherein said first plurality of dimples extendsubstantially opposite to said second plurality of dimples.
 10. Theassembly of claim 1 wherein said interconnect is a cathode-sideinterconnect.
 11. The assembly of claim 1 wherein said interconnect isan anode-side interconnect.
 12. The assembly of claim 1, wherein saidsuperstructure has a compliance of at least about 5×10⁻⁶ mm²/N.
 13. Theassembly of claim 1, wherein said superstructure has a compliance of atleast about 5×10⁻⁵ mm²/N.
 14. The assembly of claim 1, wherein saidsuperstructure has a compliance of at least about 5×10⁻⁴ mm²/N.
 15. Theassembly of claim 1, wherein said compliant superstructure is shaped toinclude at least one substantially orthogonal channel.
 16. The assemblyof claim 1, wherein said compliant superstructure is shaped to includeat least one substantially slanted channel.
 17. The assembly of claim 1,wherein said compliant superstructure is shaped to include at least onesubstantially square channel.
 18. The assembly of claim 1, wherein saidcompliant superstructure is shaped to include at least one substantiallyrectangular channel. 19 The assembly of claim 1, wherein said compliantsuperstructure is shaped to include at least one substantiallysinusoidal channel.
 20. The assembly of claim 1, wherein said compliantsuperstructure is shaped to include at least one substantiallyhour-glass shaped channel.
 21. The assembly of claim 1, wherein saidcompliant superstructure is comprised of a stainless steel, stainlesssteel alloy, or stainless steel super-alloy.
 22. The assembly of claim1, wherein said compliant superstructure is comprised of achromium-based alloy.
 23. The assembly of claim 1, wherein saidcompliant superstructure is comprised of a noble metal-based alloy. 24.The assembly of claim 1, wherein said compliant superstructure iscomprised of a composite of at least two materials.
 25. An interconnectfor a solid oxide fuel cell, comprising: a compliant superstructurehaving a first portion defining a separator plate contact zone and asecond portion defining an electrode contact zone, wherein thesuperstructure is porous to operating fuel cell gaseous materials. 26.The apparatus of claim 25, wherein said compliant superstructure iscompliant in at least three orthogonal axes.
 27. The apparatus of claim25, wherein said compliant superstructure is compliant with respect to aload applied from any direction.
 28. The apparatus of claim 25, whereinsaid compliant superstructure comprises a first plurality of compliantsubstructures disposed in a first direction and a second plurality ofcompliant substructures disposed in a second direction different fromsaid first direction so as to define a woven structure.
 29. Theapparatus of claim 28 wherein at least one compliant substructure ispre-buckled.
 30. The apparatus of claim 28 wherein said compliantsubstructures comprise wires, and wherein said woven structure is a wireweave.
 31. The apparatus of claim 28 wherein said compliantsubstructures comprise pre-buckled wires, and wherein said wovenstructure is a wire weave.
 32. The apparatus of claim 28 wherein saidcompliant superstructure is dimpled, and wherein further a firstplurality of dimples define said separator plate contact zone and asecond plurality of dimples define said electrode contact zone.
 33. Theapparatus of claim 32 wherein said first plurality of dimples extendsubstantially opposite to said second plurality of dimples.
 34. Theapparatus of claim 25 wherein said interconnect is a cathode-sideinterconnect.
 35. The apparatus of claim 25 wherein said interconnect isan anode-side interconnect.
 36. The apparatus of claim 25, wherein saidsuperstructure has a compliance of at least about 5×10⁻⁶ mm²/N.
 37. Theapparatus of claim 25, wherein said superstructure has a compliance ofat least about 5×10⁻⁵ mm²/N.
 38. The apparatus of claim 25, wherein saidsuperstructure has a compliance of at least about 5×10⁻⁴ mm²/N.
 39. Theapparatus of claim 25, wherein said compliant superstructure is shapedto include at least one substantially orthogonal channel.
 40. Theapparatus of claim 25, wherein said compliant superstructure is shapedto include at least one substantially slanted channel.
 41. The apparatusof claim 25, wherein said compliant superstructure is shaped to includeat least one substantially square channel.
 42. The apparatus of claim25, wherein said compliant superstructure is shaped to include at leastone substantially rectangular channel.
 43. The apparatus of claim 25,wherein said compliant superstructure is shaped to include at least onesubstantially sinusoidal channel.
 44. The apparatus of claim 25, whereinsaid compliant superstructure is shaped to include at least onesubstantially hour-glass shaped channel.
 45. The apparatus of claim 25,wherein said compliant superstructure is comprised of a stainless steel,stainless steel alloy, or stainless steel super-alloy.
 46. The apparatusof claim 25, wherein said compliant superstructure is comprised of achromium-based alloy.
 47. The apparatus of claim 25, wherein saidcompliant superstructure is comprised of a noble metal-based alloy. 48.The apparatus of claim 25, wherein said compliant superstructure iscomprised of a composite of at least two materials.
 49. A solid oxidefuel cell stack comprising: at least three fuel cell assemblies inelectrical contact, wherein at least one fuel cell assembly comprises anelectrode, a separator plate, and a compliant interconnect positionedbetween the electrode and the separator plate, the compliantinterconnect comprising a compliant superstructure having a firstportion defining a separator plate contact zone and a second portiondefining an electrode contact zone, wherein the superstructure is porousto operating fuel cell gaseous materials.
 50. The apparatus of claim 49,wherein said compliant superstructure is compliant in at least threeorthogonal axes.
 51. The apparatus of claim 49, wherein said compliantsuperstructure is compliant with respect to a load applied from anydirection.
 52. The apparatus of claim 49, wherein said compliantsuperstructure comprises a first plurality of compliant substructuresdisposed in a first direction and a second plurality of compliantsubstructures disposed in a second direction different from said firstdirection so as to define a woven structure.